The documents WO-A-2004/012851 and FR-A-2 872 233 disclose a device for grinding biological samples, comprising a plate forming a support for tubes containing samples to be ground and means for driving the plate in a precession movement, the plate having an axis the position of which varies by describing a cone during the precession movement.
Such a device comprises concentric bearings mounted one inside the other for supporting and centring the tube-holder plate, these bearings being disposed between an elastically suspended part of the apparatus and a drive shaft carrying the plate.
The plate is immobilised with respect to rotation about the drive shaft so that the tubes containing the samples are subjected to a high-frequency curvilinear alternating movement and so that the samples that they contain are ground and homogenised by microbeads, for example glass or ceramic, contained with the samples in the tubes.
This type of grinding is very effective and very quick but has the drawback of a fairly great increase in the temperature of the samples in the tubes. Even when the tubes containing the samples are cooled prior to grinding, the temperature of the samples at the end of grinding may attain or exceed values of around 60° to 70°, at which some characteristics of the samples are irreversibly modified. This is the case for example with proteins, the activity of which is determined both by their sequence and by their three-dimensional structure, this structure being destroyed by heating.
In order to remedy this drawback, the document WO 2008/000962 discloses a grinding device of the aforementioned type and further comprising means for cooling the tubes, comprising a bell fixed inside a foldable cover of the apparatus and means for bringing cold air inside the bell.
These cooling means make it possible to maintain the samples at a temperature of a few degrees above zero at the end of grinding, so that the three-dimensional structure of the proteins contained in these samples is not altered.
There exists a need to be able to use various types of tube with the same grinding device, for example tubes with different volumes, while guaranteeing maximum grinding efficacy for each type of tube.